Adhesive tapes which can be cleanly removed from a surface by stretching the tape are known in the prior art. The U.S. patent to Kreckel et al. U.S. Pat. No. 5,516,581, for example, discloses a removable adhesive tape strip including a highly extensible and substantially inelastic backing and a layer of pressure sensitive adhesive. When applied to a support surface, the adhesive tape strip becomes firmly bonded thereto, but can be easily removed without damaging the support surface by simply stretching the tape.
Stretch release adhesive tape strips have been used in a wide variety of applications including removably mounting a support or fixing device, such as a hook or hanger, on a wall. Conventional techniques for mounting a hook on a wall include driving a fastener, such as a nail or screw, into the wall, therefore creating a hole or otherwise damaging the wall. Stretch release adhesives tapes, in contrast, allow an item to be mounted on and removed from a wall without damaging the wall. Stretch release adhesive tape strips offer the additional advantage of working on a wide variety of wall surfaces including sheet rock, tile, and concrete, which are not well suited for conventional mounting techniques.
The U.S. patent to Hamerski et al. U.S. Pat. No. 5,507,464 discloses an article support which is adhered to a support surface using a double-sided stretch releasing adhesive. The article includes a base member, a double sided stretch release adhesive tape strip adhered to the base member, and a mechanism for gripping the stretch release adhesive tape strip. The base member and adhesive tape strip are arranged so that when the base member is adhered to the support surface by the tape, the base member can be removed by pulling on the gripping means. The U.S. patent to Luhmann, U.S. Pat. No. 5,409,189, discloses a double-sided, redetachable, self-adhesive hook including a strip of adhesive film which re-separably bonds the hook to a support surface. The adhesive power of the film largely disappears on extension of the film which is accomplished by pulling on the adhesive film. While such articles generally function satisfactorily, removal of double-sided adhesive tape strip articles can present certain difficulties. For example, where a double-sided stretch release adhesive tape strip is used to adhere an object, such as a plastic hook, to a wall, the release of the adhesive tape strip from both the object and the wall at the same time may cause the adhesive tape strip to snap-back in the direction of the stretching, in a manner similar to the snapping effect of a stretched rubber band, or may cause the object to be catapulted, particularly if the object is not held in place during removal.
Co-pending U.S. patent application Ser. No. 08/940,555, which is assigned to the same assignee as the present invention, discloses an improvement to double-sided stretchable adhesive tape strips which minimizes the problems of snap-back and catapulting by controlling the timing of the de-bonding from both the object and the support surface so that one adhesive surface releases before the other. More particularly, the adhesive tape strip includes a low adhesion portion on one surface and a greater adhesion portion on the surface opposite the low adhesion portion, whereby during removal the greater adhesion portion remains more aggressively adhered to either the support surface or the object, and the low adhesion portion completely releases from its associated surface. The low adhesion portion may be, for example, a release strip which completely de-bonds from its adhered surface prior to the complete de-bonding of the other side. Although sequentially controlling the release of the adhesive surfaces minimizes the problems of snap-back and catapulting, it does not entirely eliminate these problems. In addition, the advantages of sequential release are defeated if rebonding occurs. Rebonding occurs when the stretched adhesive tape strip re-attaches to the object or the support surface during removal and is described more fully with reference to FIGS. 1-4.
FIGS. 1-4 show an object 2 mounted on a support surface 4, such as a wall, using a stretch release adhesive tape strip 6. In FIG. 2, arrow A depicts the force applied by a user to stretch the adhesive tape strip 6, thereby to separate the object 2 from the support surface 4. As the adhesive tape strip 6 is stretched 8, its cross sectional area is reduced, (i.e. it necks down), and undergoes interfacial de-bonding 10 from both the object 2 and the support surface 4. As a result of the necking down, an open space 12 is created between the stretched adhesive tape strip 8 and both the object 2 and the support surface 4, and the adhesive tape strip 6 therefore no longer provides support for the object 2. When removed as intended, interfacial de-bonding progresses until the adhesive tape strip 6 is completely removed from the object 2 or the support surface 4, and the object 2 is therefore separated from the support surface 4.
As illustrated in FIG. 3, however, users have a tendency to apply a force B to the object 2 during removal. This causes the object 2 to contact the stretched portion 8 of the adhesive tape strip 6 and re-adhere to the stretched tape at 14. Since the tape has already been stretched, the object cannot be released by further stretching the tape. Users, however have a tendency to increase the stretch force A to the point were the adhesive tape strip breaks. Once this occurs, the object 2 must be removed from the wall 4 by either prying or violently twisting the object from the wall, often causing damage to the wall surface and/or leaving adhesive residue on the wall. Moreover, if rebonding occurs near the end of the removal sequence, that is, after most of the adhesive tape strip has been de-bonded from the object and support surface, catapulting may occur as the user continues to exert the pulling force A on the tape. If the user continues to apply force B to the object, the stretched portion 8 of the tape strip will become pinched between the object and the support surface as shown in FIG. 4 at 16. As in the case of rebonding, once the tape strip becomes pinched, users have a tendency to increase the stretch force A to the point where the adhesive tape strip breaks so that the object must pried or twisted from the wall. By eliminating rebonding and pinching, the present invention eliminates these drawbacks.